Recording apparatuses and so forth that make use of a rotating disk have grown in memory capacity in recent years, and their data transfer rates have also risen. Therefore, the bearing devices used in these recording apparatuses need to offer high reliability and performance for rotating a disk load at a high degree of accuracy. Hydrodynamic bearing devices, which are well suited to high-accuracy rotation, have been used in these recording apparatuses. Small notebook personal computers and other such mobile devices also require recording apparatuses that have higher capacity, are smaller in size, and are more resistant to impact.
With a hydrodynamic bearing device, oil or another such lubricant is interposed between a shaft and a sleeve member, pumping pressure is generated by hydrodynamic grooves during rotation, and this pressure rotates the shaft in non-contact fashion with respect to the sleeve. Because there is no contact between the shaft and the sleeve, there is no mechanical friction, which makes hydrodynamic bearing devices suited to fast and accurate rotation.